A chessboard is an 8x8 grid. If we had to create a separate variable for every square (square_a1, square_a2... square_h8), we would have 64 distinct variables that are impossible to manage. This is where data structures come in.

The List (1D Array)

Consider a single horizontal row of the chessboard (called a "rank"). We can represent it as a list. A list is an ordered sequence of elements.

• Chess: Rank 2 (the row where the 8 white pawns are initially located).
• Code: A list containing 8 elements.

Python

# Representing Rank 2 (White Pawns)
rank_2 = ["P", "P", "P", "P", "P", "P", "P", "P"] 

In Python, we define a list by enclosing a sequence of elements in square brackets [] separated by commas. Lists are ordered, indexed (starting at 0), and mutable (changeable).

Let's look at some common operations and properties of lists:

my_list = []                      # empty list
primes = [2, 3, 5, 7]             # numerical list
rank_2 = ["P", "P", "P", "P", "P", "P", "P", "P"] # list of strings
my_list = [1, "hello", 3.14]      # mixed list (heterogeneous)

# Accessing elements
print(my_list[0])                 # prints the first element of the list; 
                                  # the first element always has index 0

# Useful operations
rank_2 = ["P"] * 8                # assignment of 8 identical elements to the list
my_list.append("x")               # adds an element to the end of the list

# Measuring and Slicing
print(len(rank_2))                # displays the length (number of elements) of a list
print(rank_2[0:2])                # prints the first two elements of the list (slicing)

The Matrix (List of Lists, 2D array)

To represent the entire board, we join the rows. A chessboard is a "list of rows." In computer science, this is called a matrix or 2D array. To access a specific square in a matrix, we use two coordinates: [row][column].

Let's look at some operations and properties of matrices:

# A 3x3 matrix – a square matrix
matrix = [[1, 2, 3], [2, 1, 0], [1, 1, 1]]  

# Assignment: assign a new value to the element at position 0,0 (the first one)
matrix[0][0] = 3 

# Display the entire matrix
print(matrix) 

# Display a specific element of the matrix (Row 1, Column 2)
print(matrix[1][2])

The Indexing Problem (0 vs 1):

• In chess, rows go from 1 to 8 and columns from A to H.
• In programming, we almost always start counting from 0.
• The first row (from the top) has index 0.
• The first column (on the left) has index 0.

This requires a mental translation:

• Rank ‘1’ --> Index 7
• Rank ‘8’ --> Index 0
• Column 'A' --> Index 0
• Column 'H' --> Index 7